In the classic no-knead bread recipe, it calls for letting the dough rise once for 12-18 hours, then folding it on a work surface and letting it rise again for two hours. Why is this second rise necessary? Could I just let the bread rise once for 14-20 hours with the same effect?
The second rising is quite necessary for good, light, airy bread.
When you fold the bread and then shape it into a proper loaf, you compress it, pushing out some of the air pockets that grew when it was rising. If you don't let it rise a second time after shaping, the bread won't have the proper airy-ness and it will be very dense.
You can't shape the bread properly at the beginning, so you must do it in two steps.
I suppose that if you're OK with dense bread, you can fold and shape it and then put it right in the oven but I don't think you'll like the outcome.
I make no knead bread at least once per week. I have only skipped the second rise once...because it ruined the bread! Eek! So sad. It made it dense and flat. Definitely worth the extra time and effort to get that second rise.